Antibacterial and sunlight-driven photocatalytic activity of graphene oxide conjugated CeO2 nanoparticles

This work focuses on the structural, morphological, optical, photocatalytic, antibacterial properties of pure CeO2 nanoparticles (NPs) and graphene oxide (GO) based CeO2 nanocomposites (GO-1/CeO2, GO-5/CeO2, GO-10/CeO2, GO-15/CeO2), synthesized using the sol–gel auto-combustion and subsequent sonication method, respectively. The single-phase cubic structure of CeO2 NPs was confirmed by Rietveld refined XRD, HRTEM, FTIR and Raman spectroscopy. The average crystallite size was calculated using Debye Scherrer formula and found to increase from 20 to 25 nm for CeO2 to GO-15/CeO2 samples, respectively. The related functional groups were observed from Fourier transform infrared (FTIR) spectroscopy, consistent with the outcomes of Raman spectroscopy. The optical band gap of each sample was calculated by using a Tauc plot, which was observed to decrease from 2.8 to 1.68 eV. The valence state of Ce (Ce3+ and Ce4+) was verified using X-ray photoelectron spectroscopy (XPS) for CeO2 and GO-10/CeO2. The poisonous methylene blue (MB) dye was used to evaluate the photocatalytic activity of each sample in direct sunlight. The GO-15/CeO2 nanocomposite showed the highest photocatalytic activity with rate constant (0.01633 min–1), and it degraded the MB dye molecules by 100% within 120 min. The high photocatalytic activity of this material for degrading MB dye establishes it as an outstanding candidate for wastewater treatment. Further, these nanocomposites also demonstrated excellent antimicrobial activity against Pseudomonas aeruginosa PAO1.


Synthesis of graphene oxide (GO) nanosheets
GO was prepared successfully using a modified Hummer's method.First of all, 2 g of fine graphite powder was added to 150 ml of concentrated sulphuric acid (H 2 SO 4 ) with continuous stirring in the ice bath for 30 min.When the temperature reached 5 °C, 8 g of KMnO 4 was added very slowly to this mixture of graphite powder and H 2 SO 4 to obtain the green solution.After one hour of stirring, the sample was removed from the ice bath, and the temperature was kept constant at 35 °C with continuous stirring for 24 h.Further, 200 ml distilled water was added to dilute the mixture and left to stir for 15 min.In order to quench the reaction, 30 ml H 2 O 2 (30%) was added to the solution, stirred for 1 h, and left overnight to get precipitate.This final product was centrifuged with 200 ml HCl (10%) and H 2 O 2 (1%) solution in order to remove impurities, also with distilled water and ethanol to maintain pH ~ 7. Finally, the product was dried in a vacuum oven at 70 °C for 24 h and pulverized into a fine powder form.

Synthesis of GO-based CeO 2 nanocomposite
Graphene oxide (GO) based CeO 2 nanocomposites were systematically synthesized through a controlled sonication method.Precise amounts of GO powder, ranging from 1 to 15 wt.%, were incorporated into a 30 ml volume of deionized water and subjected to ultrasonication for 1 h, ensuring a homogenous dispersion.Subsequently, the as-synthesized CeO 2 powder was carefully introduced into the GO dispersion with gradual addition during stirring at room temperature.The resulting solution underwent an extended stirring period of 3 h to facilitate thorough integration.To conclude the synthesis, the composite solution was carefully dried in an oven at 80 °C for 24 h, promoting the removal of solvents and yielding well-defined GO-based CeO 2 nanocomposites with tailored graphene oxide concentrations.

Materials characterization
The structural properties were investigated using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction measurements (XRD), transmission electron microscopy (TEM)/high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and selected area electron diffraction (SAED) patterns.The optical properties of synthesized materials are measured using UV-visible spectroscopy, and their morphological properties are measured using a scanning electron microscope (SEM) along with EDX.Shimadzu LabX XRD-6100 Cu-k α radiation was used to generate the XRD spectra.The Rietveld refinement was carried out using the FULLPROF program to determine the crystal structure parameters of the pure CeO 2 and to confirm the single phase.Perkin Elmer spectrum-2 was used to perform FT-IR analysis on each sample to study phase purity and the functional groups.In order to further confirm vibrational frequencies obtained from FTIR, the Laser Raman spectrum has also been recorded because they are complementary to each other.To record Raman spectra, a Renishaw inVia Raman microscope with a 532 nm laser source was utilized.For the morphological study, a JEOL JEM-2100 TEM operating at 200 kV was used; the crystal structure was analyzed by means of the SAED ring network and HRTEM fringe patterns.For morphological investigation, scanning electron microscopy (SEM) was also utilized, and an energy dispersive x-ray (EDS) linked to a JEOL JSM-6510LV SEM operating at 50 kV (JEOL Co., Ltd.) was utilized for elemental analysis.The UV-Vis NIR spectrophotometer Shimadzu UV-1601 was used to measure the absorption spectra of each sample.In addition, photocatalytic activities comprising the decomposition of MB dye were studied using UV-vis absorbance spectra.

Photocatalytic activity
A 10 ppm stock solution of methylene blue (MB) dye was formed for the photocatalysis experiment in sunlight irradiation (Time: between 11:30 a.m. to 2:00 p.m., date: 18-June 2022, Place: Aligarh, India) 41 .As a control, 5 ml of an aqueous dye solution without a photocatalyst was extracted.After preparing a stock solution of MB dye in 100 ml of distilled water, 20 mg of CeO 2 NPs and their nanocomposites were added to the solution one at a time while agitating at room temperature in the presence of solar light and at various time intervals (0, 15, 30, 45, 60,  75, 90, 105, and 120 min), 5 ml samples were collected in a transparent container (0, 15, 30, 45, 60, 75, 90, 105, and 120 min).The NPs were entirely removed from the solution using centrifugation.As a result, the UV-Vis spectrophotometer was used to measure each sample's UV-Vis absorbance spectra.

Microorganisms
In the current research, Pseudomonas aeruginosa PAO1 was chosen, which was collected from the Department of Microbiology, Aligarh Muslim University, Aligarh.The bacterial culture was cultivated in nutrient broth and maintained on nutrient agar slants.

Well diffusion method
The antibacterial activity of each sample was evaluated using the well-diffusion method against pathogenic bacteria 42 .A disinfected cotton swab was utilized to spread the bacterial strain over the Mueller-Hinton agar plate.A 6-mm well was made by a sterile borer on agar.In the test, 100 µL of nanoparticles (50 μg/mL) were loaded into the wells.After that, the agar plate was incubated for 24 h at 37 °C.After 24 h of incubation, the plates were studied for the presence of a clear inhibition zone.Distilled water (sterile) was used as the negative control, and a blank well, which did not incorporate any solvent or nanomaterials, was also included.
Antibiotic susceptibility testing for P. aeruginosa PAO1 was carried out using automated microbiological systems, specifically the VITEK-2 platform.Furthermore, the investigation included P. aeruginosa POA1 strains demonstrating resistance to Amikacin, Cefepime, Ciprofloxacin, Colistin, Gentamicin, and Imipenem.

Determination of minimum inhibitory concentration (MIC)
Pure and GO-based CeO 2 nanoparticles that showed a zone of inhibition against bacteria were subjected to MIC testing.With slight modifications, the MIC of nanoparticles was calculated using the broth microdilution method 43 .A 96-well ELISA plate was used to make a two-fold serial dilution of nanoparticles in Muller-Hinton Vol:.( 1234567890 220), (311), ( 222), (400), (331) and (420) Miller planes 44 , respectively (see Fig. 1b).There is a diffraction peak of GO at angle 2θ = 10° attributed to the (001) plane.GO-based CeO 2 nanocomposite was also confirmed by the presence of both GO and CeO 2 peaks in the final composite due to the exfoliation of GO 45 .
In the XRD patterns of each sample, no extra peak was observed; also, no detectable shift of the XRD peak was obtained, which indicates that the nanocomposite was formed without any impurity.The lattice parameter (a = b = c), volume size (a 3 ), dislocation density (δ = 1/D 2 ), and lattice strain ( ε = βcosθ 4 ) were also evaluated and listed in Table 1.The ionic radii of Ce 3+ and Ce 2+ are different, so the nonlinear trends of lattice parameters have been observed in the case of all samples, as both the oxidation states of Ce can be confirmed from XPS (see Fig. 7  and 8).The lattice constant for each sample was calculated by using the following (Eq.1),where the interplanar spacing (d hkl ) can be evaluated by using Bragg's law, as expressed below (Eq.2) and (hkl) are the miller indices of the diffraction planes. (1) (2) 2d hkl Sinθ = .The average crystallite size of each sample was calculated using the Debye-Scherer formula (Eq. 3) 46 , where λ is the wavelength of the X-ray source utilized (1.541 Å), β is the full-width-at-half-maximum (FWHM) of the diffraction peak, D is the average crystallite size, and θ is the glancing angle.The value of D is found to increase from 20 to 25 nm with increasing concentration of the GO (see Table 1).The interaction between graphene oxide and cerium oxide under this synthesis condition could promote the growth of cerium oxide particles.
Because utilized synthesis conditions of the graphene oxide lead to agglomeration or clustering of particles, it might give the appearance of larger particle sizes 47 .The increased crystallite size enhances the overall surface area and catalytic activity of the nanocomposites, making them more effective in various applications, such as catalysis and antibacterial.

Fourier transform infrared (FTIR) spectroscopy
The FTIR technique is used to collect data on chemical bonds, vibrational frequencies, and the presence of functional groups and assists in figuring out the material's phase structure 48 .The FTIR spectra of each sample of synthesized materials using the KBr pellet method are shown in Fig. 2. The consistency among the spectra suggests that the CeO 2 has been successfully decorated on the GO nanosheets.The inter-atomic vibrations in oxide compounds are accounted for the absorption bands below 1000 cm -1 , which are also known as the fingerprint region of the FTIR spectra 49 .The weak Ce-O vibration in CeO 2 was indicated by the absorption peak labeled at 550 cm -150 .Additional peaks at 1350 cm -1 and 1640 cm -1 correspond to carboxylic acid's weak C-H bending vibrations and intense C=O stretching.The broad peak at 3400 cm -1 is associated with the intense O-H stretching vibration of hydroxyls from absorbed water molecules 51 .The functional groups for all GO based CeO 2 are shown in Table 2.

Raman spectroscopy
Figure 3a,b shows the Raman spectra of CeO 2 NPs and GO-10/CeO 2 nanocomposite.In the Raman spectra of CeO 2 (Fig. 3a), the strong peak at 466 cm -1 is associated with the symmetrical stretching mode of the Ce-O vibrational unit 52,53 .The two prominent peaks at 1351.7 cm -1 and 1604.7 cm -1 are shown in Raman spectra of GO-10/CeO 2 (Fig. 3b), corresponding to the D and G bands, respectively.The D band is associated with the C sp 2 atoms' in-plane vibration [52][53][54][55] , whereas the G band is related to structural defects, including bond-angle disorder, hybridization, and bond length disorder that can break the selection principles and symmetry.Defects, such as oxygen vacancies or cerium (Ce) vacancies, create additional states in the bandgap.These states act as trap sites for photoinduced electrons and holes, preventing their recombination and leading to enhanced charge carrier generation, which plays an important role in photocatalytic activity.Also defects in CeO 2 can lead to the generation of reactive oxygen species (ROS) under light irradiation.ROS, such as superoxide radicals and hydroxyl radicals, have strong antibacterial properties by inducing oxidative stress in bacteria.The blue-shifted peak at 462 cm -1 in the GO-based CeO 2 nanocomposite demonstrates that the CeO 2 nanoparticles are securely attached to the GO.The charge transfer that takes place between CeO 2 and GO is responsible for this blue shift [52][53][54] .

Transmission electron microscopy (TEM)
The morphology (particle size & their distribution), lattice fringe patterns, and ring patterns of the CeO 2 and GO (10 wt.%) based CeO 2 nanocrystalline powder sample were studied using TEM, HRTEM, and SAED techniques, respectively, as shown in Fig. 4. The TEM images shown in Fig. 4a,e corroborated the particle's spheroidal form and exhibited some distinct aggregation of nanostructured particles.Figure 4b,f analyses the HRTEM fringe patterns at higher magnification (5 nm scale) of CeO

Scanning electron microscopy (SEM)
The SEM was used for the morphological analysis of CeO 2 NPs and GO (10 wt.%) based CeO 2 nanocomposite, as shown in Fig. 5a and b, with the appropriate scale indication at 10 and 5 µm, respectively.The optical, electronic, and structural properties of nanocrystalline materials can be affected by their morphology.In SEM images, the grains appeared to be of different sizes and shapes along with agglomerated nanocrystallites.CeO 2 showed the agglomeration of synthesized nanoparticles (Fig. 5a).The nanocomposites showed CeO 2 nanoparticles to be enclosed, attached, and of a porous nature (Fig. 5b).Additionally, it can be seen from the micrographs that the grain sizes get smaller with GO, which is in good agreement with the findings from XRD and TEM.Additionally, the formation of polycrystalline grains from the fusing of several crystallites may account for the variation in crystallite or grain size 57 .It has come to conclude that every sample is uniformly dense, has good crystal quality, and is free of any microscopic defects in the grains.
As shown in Fig. 5c and d, the chemical and elemental composition of CeO 2 and GO (10 wt.%) based CeO 2 was also examined using EDX connected to SEM.The attached tables in the insets of Fig. 5c and d showed the elemental compositions by weight percent and atomic percent, and the spectra showed that in the synthesized

UV-visible spectroscopy
As shown in Fig. 6, optical absorbance spectra of the synthesized samples were performed using a double-beam UV-Vis spectrophotometer to study the photocatalytic activities and optical properties of these samples.In Fig. 6a, the absorbance at 340 nm is caused by the scattering effect of the randomly organized grain boundaries and nanocrystallites.The average crystallite size was increased with the incorporation of GO nanosheets, which was concomitant with the decreasing behavior of the optical band gap (from 2.8 to 1.68 eV) due to the quantum confinement effect.With the increased GO concentration, a slight red-shift was seen in the absorbance edge, indicating a corresponding contraction of the band gap 59 as shown in Table 1.In order to be a promising photocatalyst and exhibit effective photocatalytic properties, the material must be optically active (to produce  electron-hole pairs).CeO 2 is a direct band gap semiconductor.So, we utilized this Tauc equation for calculating the band gap for n = 1/2.As shown in Fig. 6b, the optical energy band gap E g of the synthesized sample was calculated using Tauc's plot and the relation (Eq.4). where Here, hv, B, E g , α, t, and A are the energy of an absorbed photon in eV, energy independent constant, band gap, the coefficient of the absorption (Eq.5), quartz cuvette thickness (10 mm), and sample absorbance, respectively.

X-ray photoelectron spectroscopy (XPS)
The surface elemental compositions of CeO 2 and GO-10/CeO 2 are further studied by using XPS, which confirms that the sample contains cerium, carbon, and oxygen elements without other impurities, as can be seen in Fig. 7,  8.The analysis of the CeO 2 and GO-10/CeO 2 nanocomposite spectra showed the presence of Ce 3d, C 1 s, and O 1 s in Fig. 7 and 8, respectively.The spin-orbit splitting of Ce 3d 5/2 and Ce 3d 3/2 60 might account for eight peaks in the high-resolution spectra of Ce 3d (Fig. 7b and 8b).Consequently, CeO 2 and its nanocomposite include both oxidation states Ce 3+ and Ce 4+ due to spin doublet splitting 61 32 .At (885.3 and 903.7 eV) and (886.3 and 901.6 eV) for CeO 2 and its nanocomposite, respectively, the XPS peaks correspond to the valence state of Ce 3+62 .Both Ce 3+ and Ce 4+ oxidation states can play distinct roles in photocatalytic phenomena.Ce 3+ is often involved in redox mediation and electron scavenging, while Ce 4+ can act as an electron acceptor, contributing to the overall efficiency of photocatalytic processes.The specific benefits depend on the photocatalytic system and the reaction involved.
The intense peaks at 529.6 and 529.8 eV, in the high-resolution O 1 s XPS (Fig. 7c, 8c), are related to lattice O of CeO 2 and GO-10/CeO 2 , respectively 63 ; however, the high BE (530.4 eV and 532.1 eV) and (530.8And 532.8 eV) peaks may be due to hydroxyl or water or loosely bound adsorbed oxygen present in the unoccupied sites of the lattice and also due to oxygen deficiency region inside CeO 2 matrix (O attached to Ce 3+ ).Two peaks with BE values of (284.6 and 289.2 eV) and (284.0 and 285.7 eV) were fitted to CeO 2 and GO-10/CeO 2 C 1 s spectra, corresponding to sp 2 bonded carbon C-C and N-C=N bonds, respectively (see Fig. 7d, 8d) 64 .

Photocatalytic activity
Wastewater treatment by using the photocatalytic technique is described as follows: About 20 mg of photocatalysts, CeO 2 , and its GO (1, 5, 10, and 15 wt.%) based nanocomposites were mixed throughout a solution of 1000 mL distilled water containing 10 mg of methylene blue (MB) dye.The pH of the solution was set to be around 7 after degradation.This solution was vigorously stirred for 30 min in the dark to attain a state of equilibrium between the photocatalyst and dye.Sunlight was thrown into this solution while it was being stirred after the adsorption and desorption processes had reached equilibrium.A Small amount of the solution was taken after a predetermined period of time.Centrifugation was employed to separate the photocatalyst from the treated solution, and UV-vis measurements of dye degradation were recorded using a spectrophotometer.The procedure was repeated to complete the degradation of MB dye, and no further absorption peak could be detected.
Figure 9a-e shows the UV-Vis absorption spectra with photocatalysts CeO 2 and GO-based CeO 2 nanocomposites for MB dye degradation after exposure to sunlight for different time intervals.The absorption peaks at 663 nm 65 for MB dye degradation show that as the exposure duration of sunlight to solution increases, the intensity of peaks decreases, indicating the degradation of MB dye in the presence of sunlight.When the sun radiation with a proper amount of energy (comparable to or greater than the energy of the band gap) reaches the surface of the photocatalyst, electron-hole pairs are produced, which are required to start the photocatalytic process.The excited electrons in the conduction band and holes in the valence band react with nearby oxygen (O 2 ) molecules and surface-bound water molecules to create superoxide radical anion ( Ȯ− 2 ) and hydroxyl radical www.nature.com/scientificreports/( ȮH ).Free radicals shown in equation (Eq.6) are referred to as ROS (reactive oxygen species) 66 .They react quickly with organic pollutants to break them apart 67 , and Fig. 10 shows the mechanism of photocatalytic activity.www.nature.com/scientificreports/It is possible to use this photocatalyst to degrade all dyes, such as methyl red, rhodamine B, congo red, methyl orange, methyl violet, acid Blue 80, malachite green, etc., that are susceptible to degradation in the presence of these reactive radicals 68 .
The photocatalyst can be separated from the solution by centrifugation once the MB dye has been entirely degraded.Figure 11a shows how the "degradation efficiency" (C/C o ) of the MB dye with time.The increased photocatalytic activity with increasing GO concentration may be due to the following reasons: (i) due to the emergence of generalized localized states, photon absorption increases, and (ii) higher concentrations of oxygen vacancy, which serve as energy traps and slow down recombination of electron-hole pair 52 .
Oxygen vacancies reduced electron-hole recombination and enhanced the photocatalytic activity of CeO 2 NPs and GO-based CeO 2 nanocomposites 69 .As shown in Fig. 11b, a pure CeO 2 photocatalyst degrades the MB dye up to 50%, while GO (1, 5, 10, and 15 wt%) based CeO 2 photocatalysts degrade 64%, 66%, 90%, and 100% (Table 3), respectively.Here it can be noted that 15% GO-based CeO 2 nanocomposite is the best photocatalyst to treat the MB dye present in wastewater.
The following expression (Eq.7) was used to determine the proportion of MB dye that was degraded due to the presence of photocatalysts, where C 0 and C t represent MB dye concentration at 0 min and 120 min, respectively, before and after degradation.The MB dye photocatalytic degradation reaction rate constant, k, was calculated using pseudo-first-order rate kinetics.The pseudo-first-order kinetic model is commonly used to describe the kinetics of photocatalytic reactions.In the context of photocatalytic activity, this model is often applied to describe the degradation or transformation of a target compound (e.g.MB dye) under the influence of a photocatalyst (e.g.CeO 2 and GO-based CeO 2 nanocomposites).The natural logarithmic transformation of the concentration ratio ( ln C 0 C t ) on the y-axis results in a linear relationship with time (t) on x-axis.This linear fitting allows for easier analysis and determination of the pseudo-first-order rate constant, i.e., equal to the value of the observed slope.It can be explained by the following expression (Eqs.8 and 9), As seen in Fig. 12a-e, the rate constants for CeO 2 and GO (1, 5, 10, and 15% wt.%) based CeO 2 were found to be 0.00471, 0.00714, 0.00707, 0.01569, and 0.01633 min -1 , respectively.Faster photodegradation of MB dye is attributed to the presence of GO (15 wt.%) because of the suppression of the electron-hole pair recombination rate caused by the development of localized energy states and oxygen vacancies 70 .

Determination of zone of inhibition
Nanoparticles were evaluated for antibacterial efficacy against pathogenic bacteria PAO1 using the well-diffusion method.Table 4 shows the results of the antibacterial activity evaluation of nanoparticles.According to the findings, some nanoparticles were potentially beneficial in reducing bacterial development (Fig. 13).

Determination of MIC
The antibacterial actions of nanoparticles on bacteria are summarized in Table 4.The microbiological sensitivity to the various nanoparticles shown by the mean MIC values ranged from 10 to 20 µg/mL.

Conclusion
In conclusion, the high-performance photocatalysts CeO 2 NPs and GO (1, 5, 10, and 15 wt.%) based CeO 2 nanocomposite were successfully synthesized.The HRTEM, Rietveld refined XRD, Raman spectra, and SAED were used to confirm the single-phase cubic structure of the synthesized materials, and no possible impurities were identified.The average crystallite size was increased with the incorporation of GO nanosheets, which was concomitant with the decreasing behavior of the optical band gap (from 2.8 to 1.68 eV) due to the quantum confinement effect.The FT-IR and Raman analysis confirmed the presence of Ce-O bond and other vibrational  modes in each sample.The aggregation of nanoparticles with some porosity in GO-based CeO 2 nanocomposites was measured in the SEM micrographs.Ce 3+ /Ce 4+ valence states and the presence of oxygen vacancies were confirmed using XPS measurement.Furthermore, enhanced photocatalytic and antibacterial activities were observed due to the increasing concentration of GO in the pure CeO 2 NPs because of the formation of oxygen vacancies and localized energy states that slow the recombination rate of electron-hole pairs.The highest rate constant (k = 0.01633 min -1 ) was calculated for GO-15/CeO 2 , which degraded the MB dye from wastewater up to 100% in 120 min under sunlight irradiation.Again, these nanocomposites also showed excellent antibacterial activity against Pseudomonas aeruginosa PAO1.In particular, these materials could be used in the development of new antibacterial coatings for medical devices, implants, and wound dressings, along with industrial wastewater treatment.

Figure 6 .
Figure 6.(a) UV-vis absorbance spectra of all synthesized materials.(b) Tauc plot for energy band gap calculation of each sample.

Figure 7 .
Figure 7. XPS (a) full scan spectrum, narrow scan spectra of (b) Ce 3d, (c) O 1 s and (d) C 1 s energy level of CeO 2 NPs.

Figure 10 .
Figure 10.Mechanism of photodegradation of MB dye using synthesized materials.

Figure 11 .
Figure 11.(a) C/C o vs time spectra for pure CeO 2 NPs and GO (1, 5, 10 and 15 wt.%) based CeO 2 , and (b) Bar diagram of percent degradation vs GO concentration for all synthesized materials.

Results and discussion X-ray diffraction
)

Table 1 .
Lattice parameter, unit cell volume, dislocation density, strain, average crystallite size, and energy band gap for all synthesized samples.

Table 2 .
Functional group for all synthesized materials.
Ce-O-Ce C-H C=O O-H Vol:.(1234567890)Scientific Reports | (2024) 14:6606 | https://doi.org/10.1038/s41598-024-54905-0 56nd GO (10 wt.%) based CeO 2 , and the insets show the zoomed area of fringe patterns.The measured d-spacings in two directions were 2.93 and 1.84 nm, indicating the (200) and (220) Miller planes of CeO 2 .Figure4c,g SAED patterns depict ring networks composed of distinct patches, indicating the polycrystalline nanostructure of both pure and GO (10 wt.%)-based CeO 2 .Particle sizes for the sample CeO 2 and GO (10 wt.%) based CeO 2 were found to be 23 nm and 25 nm, respectively, which is in good agreement with the XRD data, as shown in Fig.4d,h which displays the curves for the distribution of particle size fitted by Gaussian distribution.According to HRTEM and SAED patterns, all compositions have a cubic bixbyite structure, which is explained by the observed d-spacings and planes56.

Table 3 .
Degradation of MB dye using different photocatalysts and antibacterial activity obtained from previous studies.

Table 4 .
Nanoparticles with their zone of inhibition (mm) and MIC (µg/mL) value against the pathogenic bacteria.(-) not determined. S.